Field of the Invention
The present invention relates to what is called an equipment front end module system (which will be hereinafter referred to as an EFEM system), which is used in a semiconductor manufacturing process or the like when transferring wafers stored in an airtight transfer container called a pod to a semiconductor processing apparatus and transferring wafers from the semiconductor processing apparatus to the pod. The present invention also relates to a load port unit used in the EFEM system to open and close the lid of the pod.
Description of the Related Art
In semiconductor manufacturing processes in recent years, there have been widely used a method of keeping a highly clean condition only in the interior of three spaces including the interior of processing apparatuses, the interior of pods in which wafers are stored to enable transfer of the wafers between processing apparatuses, and a mini environment (or small space) through which the wafers are transferred between a pod and each processing apparatus, thereby controlling the cleanliness throughout the process. The pod as such is a container composed of a body in which wafers are stored and that has an opening provided on one side thereof through which wafers are brought into/out of it, and a lid for closing the opening to seal the interior space of the pod. The mini environment has an opening portion that can be opposed to the opening of the pod, and a second opening portion provided on the semiconductor processing apparatus side opposite to the opening portion.
The mini environment is supplied with environmental air which is cleaned using a filter. The aforementioned apparatus used to open and close the lid of the pod, the mini environment, and a wafer transfer system provided in the mini environment are collectively called an EFEM system. In the EFEM system, the cleanness of the mini environment is kept to a predetermined level by the use of clean air supplied through the filter. With miniaturization and improvement in the performance of semiconductor devices in recent years, wiring patterns used in semiconductor devices have become finer, and it is required more strictly to prevent the patterns from being affected by oxidation. For this reason, systems in which the mini environment is constructed as a closed space in which nitrogen atmosphere having a purity higher than a predetermined level is maintained, as disclosed in Japanese Patent No. 4301456 and Japanese patent No. 4309935, have been employed increasingly.